Certain medical conditions require immediate injection of medication. The condition requiring such treatment may result from a variety of causes. Among the most serious of those conditions is anaphylaxis (a severe allergic reaction) that, in many cases, can become fatal within minutes if left untreated. Among the numerous allergens that may cause anaphylaxis are insect bites, various chemical substances and foods. Food products having even small quantities of peanuts, seafood or milk products can, in some individuals, induce severe, potentially lethal reactions. In foods, the allergen may be “hidden”, that is, the food, unknowingly, may contain a minute trace of an allergenic ingredient or may have been exposed to the allergenic ingredient during its processing. When anaphylaxis occurs, often there is insufficient time for the patient to reach a hospital or other trained and equipped medical personnel.
Individuals known to be at risk for anaphylactic reaction typically are advised to carry, at all times, an auto-injection device adapted to inject a bolus of epinephrine. The ability to inject the epinephrine immediately can be a matter of life or death. Notwithstanding the severe risk involved, there is evidence that a large proportion of the population that should be carrying such a device, in fact, does not. At least one study indicates that fewer than 30% of patients at risk of anaphylaxis carry the device at all times. See Goldberg A, Confino-Cohen R., “Insect Sting-Inflicted Systemic Reactions: Attitudes of Patients With Insect Venom Allergy Regarding After-Sting Behavior and Proper Administration of Epinephrine”, J Allergy Clin Immonol 2000; 106: 1184-9. Food based allergies are reported to cause anaphylactic reactions resulting in 30,000 trips to the emergency room and 150 to 200 deaths per year (www.foodallergy.com). The main factor contributing to a fatal outcome is the fact that the victims did not carry their emergency kit with adrenaline (epinephrine). See Wuthrich, B., “Lethal or Life Threatening Allergic Reactions to Food”, J. Investig Allergol Clin Immunol, 2000 March-April, 10 (2): 59-65. Moreover, even for those individuals that are required to carry such a device, it has been reported that a large proportion (as much as two-thirds) are insufficiently familiar with its use and operation. See Sicherer, S. H., Forman, J. A., Noone, S. A., “Use Assessment of Self-Administered Epinephrine Among Food-Allergic Children and Pediatricians”, Pediatrics, 2000; 105: 359-362. Only 25% of physicians, in one study, were able to properly demonstrate the use of the device. See Grouhi, M., Alsherhri, M., Hummel, D, Roifman, C. M., “Anaphylaxis and Epinephrine Auto-injector Training: Who Will Teach the Teachers?, Journal of Allergy and Clinical Immunology 1999 July; 104 (1): 190-3. It has been estimated that as many as forty million individuals in the United States are at risk of anaphylaxis. See Neugut, A. I., Ghatak, A. T., and Miller, R. L., “Anaphylaxis in the United States: An Investigation into its Epidemiology”, Archives of Internal Medicine 2001 Jan. 8; 161 (1): 15-21.
Perhaps the most common automatic emergency epinephrine injection device is commercially available from DEY, Inc. of Napa, Calif. under the trade designation EpiPen. The EpiPen device, believed to be described in U.S. Pat. No. 4,031,893, is designed to inject rapidly an adult dose of about 0.30 milligrams of epinephrine. The device is generally tubular and, including its tubular container, is about six inches long and nearly one inch in diameter. The device is relatively bulky and requires several manipulative steps in its use. Where a patient may only actually use the device infrequently, there may be some confusion in performing the required manipulative steps, particularly when the individual experiencing an anaphylactic reaction may be in a state of near panic. Although the device includes written instructions on its cylindrical surface, they may not be easily read, particularly under the stress of emergency circumstances. The manner in which the EpiPen is to be used is not readily and intuitively apparent without reading the text of the instructions on the cylindrical sleeve. Should it be necessary for someone other than the patient (e.g., a bystander) to administer the medication, for example, if the patient has gone into shock, the person called on to administer the medication may not know how to operate the auto-injection device. Consequently, precious time may be lost, increasing the risk to the patient. Additionally, after the device has been used to effect an injection, its hypodermic needle remains exposed, presenting post-injection hazards. Among such hazards are those associated with blood-born diseases such as HIV and hepatitis B and C or, when some of the medication remains in the device after injection, the risk of delivering some of the residual medication as a consequence of an accidental needle stick.
It would be desirable to provide a more compact, low profile, easily used auto-injector for rapid transcutaneous administration of a predetermined dose of medication.